The present invention relates to a thrust bearing having a sliding face on each of both sides thereof (which is hereinafter referred to as a double-sided sliding thrust bearing), which has a plate shape and both the faces of which are in sliding contact with counterparts.
As a bearing which is formed into a plate shape and both the faces of which are in sliding contact with counterparts, a double-sided sliding thrust bearing is known. This double-sided sliding thrust bearing is used as, for example, a swash plate of a swash plate type piston pump (variable type pump, and compressor etc.) and etc. In the swash plate type piston pump, a gas in a cylinder is compressed by a piston reciprocated in the cylinder while following the rotating swash plate, and the swash plate slides with respect to a shoe which is a counterpart interposed between the swash plate and the piston. The swash plate of the swash plate type piston pump is rotated at a high speed, and is also subjected to a high pressure by the shoe.
Conventionally, in the double-sided sliding thrust bearing used in an equipment such as a swash plate type compressor, a sliding layer with a thickness of about 2 to 20 μm is provided by coating one time or a plurality of times both faces of a base member with a synthetic resin, or the double-sided sliding thrust bearing itself is made of a simple substance of resin.
On the other hand, in the double-sided sliding thrust bearing, a lubricant is supplied onto the sliding faces thereof. In particular, in the swash plate type compressor etc., the mixture of a refrigerant and a refrigerator oil, which is the lubricant, (refrigerant/refrigerator-oil mixture) is supplied. The lubricant is supplied onto the sliding faces of the double-sided sliding thrust bearing, however, in the case of an equipment which is sometimes not used for a long period of time as in the case of a compressor for an air conditioner, the refrigerant/refrigerator oil mixture comes not to be present on the sliding faces of the double-sided sliding thrust bearing with the result that a dry state is caused. In the case where the compressor is started in this dry state, since a certain time comes to be necessary until the refrigerant/refrigerator-oil mixture is supplied onto the sliding faces, sliding occurs in the dry state during a period before the refrigerant/refrigerator oil mixture comes to be supplied with the result that seizure is apt to be caused due to a high load applied to the double-sided sliding thrust bearing. Therefore, a double-sided sliding thrust bearing is required to be able to slide counterparts for a long time without any occurrence of seizing even in the dry state before the refrigerant/refrigerator-oil mixture is supplied sufficiently.